Rep. Lauren Underwood, D-Naperville, took part in a Committee on Homeland Security hearing during which she questioned Homeland Security Secretary Kirstjen Nielsen about the separating of migrant children from their families after crossing the U.S.-Mexico border.

The Trump administration enforced a "zero-tolerance" policy to criminally prosecute all adults caught crossing the border illegally, which lead to children being separated from their families. After pressure from human rights advocates and some allies, President Donald Trump ended the policy last June.

As a former nurse, Underwood said she would question Nielsen about the potential harm caused to hundreds of children affected by the policy.

"Madam Secretary, I want to be very clear about what the family separation policy is doing to childrens' mental and physical health," Underwood said in her opening statement. "And I want to know if DHS even considered their health when developing these policies."

Underwood also asked if DHS knew separating children could cause trauma and long-term health effects. Nielsen said she was aware "trauma is part of the journey to come up to the border illegally."

"From what I've heard today, I'm not sure if the Department of Homeland Security was so negligent they didn't know how traumatic family separation was for children of if they knew and did it anyway," Underwood said. "Both are unacceptable."